<!DOCTYPE html>
<html>
  <head>
    <style>
      html {
        background-color: #ccc;
        font-size: 50px;
      }
      .frame {
        text-align: center;
      }
      .left {
        float: left;
      }
      .narrow {
        width: 300px;
      }
      .wide {
        width: 600px;
      }
      .short {
        height: 360px;
      }
      .tall {
        height: 800px;
      }
      iframe {
        width: 300px;
        border: solid 1px black;
        display: block;
        background-color: white;
      }
      .wide iframe {
        width: 600px;
      }
      .tall iframe {
        height: 660px;
      }
      .short iframe {
        height: 300px;
      }
    </style>
  </head>
  <body>
    <div class="frame tall left wide">
      <iframe id="frameone" sandbox="allow-scripts" src="summit-one.html">
      </iframe>
      frame one
    </div>
    <div class="left">
      <div class="frame short narrow">
        <iframe id="frametwo" sandbox="allow-scripts" src="summit-two.html">
        </iframe>
        frame two
      </div>
      <div class="frame short narrow">
        <iframe id="framethree" sandbox="allow-scripts" src="summit-three.html">
        </iframe>
        frame three
      </div>
    </div>
  </body>
</html>
